Digital transmission method for bandwidth and bit rate flexibility

ABSTRACT

The invention relates to AC coding. The phase angle or the duration of pulses are marked by half-periods or periods and are then provided as stages. The aim of the present invention is to flexibly adjust the bandwidths and bit rates. The number of filler elements that are allocated to the active code elements is increased or reduced. Bit rate flexibility is obtained by increasing or reducing the positions or stages or by configuring the code elements of virtual code words in a serial manner in relation to code words for transmitting information, whereby said code elements are arranged in parallel.

This application is a 371 of PCT/EP00/12058 filed on Dec. 1, 2000.

TECHNICAL FIELD

The present invention is concerned with the digital transmission ofinformation, especially various types of information over only onetransmission path, such as cable, radio or light waveguides.

BACKGROUND OF THE INVENTION

In order to send various types of information (such as high speed data,data, digital speech) over only one transmission channel, theAsynchronous Transfer Mode (ATM) was developed in which the useful andcontrol information of a source are arranged in cells in a packetingdevice and provided with a header. In asynchronous time multiples, thevarious types of information are transmitted over one transmission path.The expenditure of hardware for this technology is very great. Celloverhauling required additional resequencing mechanisms, for example.Since a header must be provided for each cell, a great part of thetransmission capacity is already used for this.

SUMMARY OF THE INVENTION

In accordance with the invention, serial channels are constructed out ofeach binary code element of the code words to be transmitted (virtualcode words), in which the channels are provided binary coded code wordsof the respective information.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 represents an arrangement of the virtual code words (I, II, III,. . . ) and the real code words (1, 2, 3, . . . ) in accordance with thepresent invention;

FIGS. 2, 3 and 6 show the principle of phase and duration pulse coding,

FIGS. 4, and 5 show the principle of the envelope curves and with asmooth amplitude transition,

FIG. 7 shows application of the invention in relation to singlesideband, and

FIGS. 8 and 9 show a radio relay system conventionally and in accordancewith the invention.

The principle of the invention will be explained in more detail withreference to FIG. 1. The binary arranged code words I, II, III, IV, I,II, . . . , designated as virtual code words, are transmitted with anydesired code over cable, radio or light wave guides. For the encoding,there can be provided a PSK or QAM code, or a code in which only onealternating current of one frequency and phase is sent in an unbrokensequence. This will be described hereinafter with reference to FIGS. 2,3 and 6. In FIG. 1, serial channels 1–12 are constructed out of thebinary code elements 1p–12p. The binary coded information to betransmitted is arranged serially in the channels, e.g. an 8 bit pickupof a speech channel with the code elementsI/1p-II/1p-III/1p-IV/1p-I/1p-II/1p-III/1p-IV/1p.

Parallel/serial converters are known and therefore will not be describedfurther. The real serially arranged code codes can have any magnitudeand can be divided into one, two or several channels. The same goes forthe code elements. Naturally, the type of information and the channelreservation must be imparted to the receiving station. The band widthand bit count can be established especially flexibly, is an alternatingcurrent of one frequency and one phase length is provided as code, inwhich the steps are constructed with respect to each other as adifferent size duration of periods or count of periods or differentphaselengths of periods. A change is thereby also made by a change ofthe frequency of the code-alternating current.

Hereafter the relationships in digital coding will be explained, andthen the phase- and the impulse-duration principle of the coding withone alternating current of one frequency and phase.

The methods on which this invention is based will firstly be describedin greater detail. The greater the number of stages or steps in thecode, the more information that can be transmitted, as can be seen fromthe following table:

No of stages: No of places: Combinations: Bits: 2 2/3/4/5 4/8/16/322/3/4/5 3 ″ 9/27/81/243 3/4/6/7 4 ″ 16/64/256/1024 4/6/8/10 5 ″25/125/625/3125 4/6/9/11 6 ″ 36/216/1296/7776 5/7/10/12

If 2 90°-phase-shifted alternating currents of the same frequency, whichare added for the transmission (OAM), are used for encoding, that gives4×4=16 stages.

In the case of carrier frequency transmission because of the ⅙ power itis advantageously possible to use the single sideband method. As inaccordance with the carrier formula:

${\mu_{AM}(t)} = {{{{\overset{\_}{\mu}}_{T} \cdot \sin}\;\omega_{T}t} + {{\frac{m}{2} \cdot {\overset{\_}{\mu}}_{T} \cdot {\cos( {\omega_{T} - \omega_{M}} )}}t} - {{\frac{m}{2} \cdot \overset{\_}{\mu_{T}} \cdot {\cos( {\omega_{T} + \omega_{M}} )}}t}}$the modulation amplitude is not also involved in the frequency, thataffords narrow-band transmission.

The Phase Principle (described in U.S. Pat. No. 5,587,797):

With this principle the phase positions of pulses for example withrespect to a reference pulse or the positive or negative difference withrespect to the preceding pulse are provided as stages or steps. In FIG.6 the reference phase is the pulse B1, B2, B3, . . . . As FIG. 6 a showsthe pulses Bn1, Bn2, Bn3 are phase-shifted by the amount n. In FIG. 6 bthe pulses BN1, BN2, BN3 involve the same phase. That phase code wouldtherefore have 2 stages Bn and BN. Those pulses are represented byintegral half-periods or periods of the same frequency.

FIG. 2 shows such an encoding situation. 4 periods are associated withthe reference pulse. The first pulse BNp therefore has 4 periods. If thefollowing pulse should be trailing, it must have 5 periods. The secondpulse Bnn therefore trails by the amount n. If the third pulse shouldremain trailing, it must contain 4 periods. The fourth pulse shouldagain be in phase with the reference pulse, this is achieved in that ithas a period fewer, that is to say 3 periods. It will also be seen thateach following pulse has a change in amplitude. A doubling in the numberof stages can be achieved by the pulses being caused to begin on the onehand with a positive half-period and on the other hand with a negativehalf-period. This is shown hatched in the drawing. That therefore thengives at place 2, 4 stages (European patent No 0 953 246 B1 and U.S.Pat. No. 6,463,104B1).

The Pulse Duration Principle (as described in U.S. Pat. No. 6,072,829):

This principle involves using various pulse durations or pulse durationdifferences as stages or steps. FIG. 3 shows 3 pulse durations, D1, D2and D3, that is to say 3 stages. It also represents a code word having 3places or digits. The place 1 can occupy the stages D1, D2, D3, theplace 2 can occupy the stages D2, D1, D3 and the place 3 can occupy thestages D3, D1, D2. With 3 stages and 3 places that gives 3 to the power3 combinations, that is to say 3×3×3=27 combinations. If in addition thepositive and negative beginning of the stages or code elements are used,that gives 6 stages. With 3 places, that then gives 216 combinations.QAM can also be used. The encoding alternating current can also beprovided as a transmission alternating current.

How is the feature ‘flexibility of the band widths’ which isparticularly emphasised in the ATM procedure achieved with the presentmethods? That can be done in a very very simple way. The changes inamplitude also give rise to an envelope curve. FIG. 4 shows such a curvewith 2 and 3 periods as stages. In this case fH is the envelope curve.In FIG. 5 in contrast the stages are 11, 12 and 11, 12, 13 periods. Inthe case of both stages, there are 10 periods as filling elements. Itwill be seen there that the frequency of the envelope curve is muchsmaller, that is to say the band width is also smaller. The band widthcan therefore be determined by means of the filling elements. This doesnot require any change in the encoding frequency.

As regards also the bit rates, these can be controlled in a highlyflexible manner. It will be apparent from FIGS. 2, 3 and 6 that it ispossible to provide any amount of stages without the encoding frequencyhaving to be altered. Depending on the respective transmission mode,speech, data images, the code words can be accurately matched to therequired number of bits, and that naturally also applies in regard toATM.

In order to demonstrate how great the information density is with thatmethod, a comparison is made with a radio relay system, the circuit inprinciple of which is shown in FIG. 8. This is designed for 34.368Mbits. The band width is 1700–2100 MHz with 4 PSK encoding. It will beseen that the hardware is very expensive. With a code as shown in FIG.2, 3, 6 or 4 the predetermined band width would not be sufficient.Filling elements therefore have to be provided. With 4 stages with 10,11, 12 and 13 periods on average 11.5 periods are required for a codeelement. For a 4-digit code word 4×11.5=46 periods are then required.Assuming that 1900 MHz is the encoding frequency, that then gives1900:46=41.3 M code words/s. With one code word there is 4 to the power4=256 combinations, that is to say 8 bits. With 41.3 M code words thatis 41.3×8=330 Mbits/s. That therefore involves 9.6 times more bits thanin the conventional radio relay system. With a doubling of the stages,as set forth in FIG. 2, that then gives 8 stages. With 4 places thatgives 8 to the power 4=4096 combinations=12 bits. With 41.3 code wordsthat is 495.6 Mbits/s. That is 14.4 times as many as in the radio relaysystem involving conventional encoding. If the encoding procedureinvolves the use of 2 alternating currents at 1900 MHz which arephase-shifted relative to each other through 90° and which are addedupon transmission (OAM), that gives 8×8=64 stages. With a code wordinvolving 2 places, that gives 12 bits. Then on average 23 periods arenecessary per code word so that at 1900 MHz 82.6 M code words areobtained, this is then 991 Mbits/s, that is to say 28.8 times more thanin the radio relay system. Counting members are primarily required inthe encoding and decoding procedures. FIG. 9 shows the principle of aradio relay system according to the invention. The signal arriving withthe HDB3 code is converted in the code converter into the code accordingto the invention and forwarded directly to the transmitting amplifier Vrand to the antenna.

FIG. 1 shows encoding of colour television signals. Associated with theluminance tappings L are 8 bits. Allocated to 4 luminance tappings ineach case is one colour tapping I/Q or red/blue each with 6 bits. Those12 bits are then attached to the 4×8 bits of the luminance values. Inaddition 1 bit for control signals and speech is also associated witheach luminance tapping. Therefore 12 bits must be encoded per tapping.Therefore one carrier is sufficient for transmission.

Another method of band width and bit rate flexibility is also set forthhereinafter, which will be described in greater detail with reference toFIG. 1. As can be seen from that Figure, all colour television signalsare encoded with 12 bits and transmitted. As the tapping of the coloursignals is slower than that of the luminance signals, they aredistributed with intermediate storage to 4 luminance values. If anotherkind of information is to be transmitted after conclusion of the colourtelevision transmission, redundancy losses are to be reckoned to occurwith the previous encoding procedures. FIG. 1 shows a method with whichthose disadvantages do not occur. In this respect the code words I, II,III, . . . are in the form of virtual code words. They are alsotransmitted at a predetermined frequency. In this case, associated witheach parallel code element 1p to 12p is a channel, that is to say thechannels 1 to 12 for the 12 code elements 1p to 12p. Code words aretherefore formed serially, for example I1p, II1p, III1p, IV1p, I1p, . .. . In the case of speech 8 code elements would be serially required.Those code words can assume any size. It is only the kind of informationto be transmitted that is important. The serially arranged code wordsare then obtained by means of a parallel/serial converter. With memoriesand multiplexers it is then possible for example for all 12 channels tobe occupied, in that case each channel can transmit code words ofdifferent sizes.

It is possible with this method to achieve band width flexibility andbit rate flexibility without involvement in the hardware. Thetransmission paths are put to optimum use. Together with the wavelengthmultiplex method it is thought that the band width deficiency isovercome thereby for the foreseeable future.

Encoding of the information of the respective channel can be effectedwith an encoding alternating current. For that purpose it is alsopossible to provide two alternating currents of the same frequency,which are phase-shifted through 90° relative to each other and added forthe transmission. It will be appreciated that it is possible to providetwo alternating currents involving the same phase if they are modulatedfor the transmission on to two 90° phase-shifted carriers. They are thenalso added.

1. A digital transmission method for combining a plurality of channelshaving the same or different kinds of information, for transmission overa single transmission medium, said method comprising: forming virtualcode words from a plurality of parallel code elements, wherein each ofsaid parallel code elements occupies a respective bit position in saidvirtual code words, and each of the bit positions is associated with oneof said plurality of channels and kind of information to be transmitted;encoding and transmitting said virtual code words using said singletransmission medium; and reconstructing said plurality of channels byforming code words from said parallel code elements occupying the samebit positions in a plurality of virtual code words.
 2. The method ofclaim 1, wherein said code words formed from said parallel code elementsfor each respective channel contain different numbers of said parallelcode elements.
 3. The method of claim 1, wherein said code words areformed from said parallel code elements occupying a plurality of samebit positions in a plurality of virtual code words.
 4. The method ofclaim 1, further comprising providing a first alternating current,having a constant frequency and first phase for the encoding andtransmission of said virtual code words, wherein said code elements aresent in an uninterrupted series.
 5. The method of claim 4, wherein saidcode elements are created based on characteristics of said firstalternating current, wherein said characteristics of said firstalternating current are selected from the group consisting of the countof like magnitude periods, the count of like magnitude half-periods, theduration of like magnitude periods, the duration of like magnitudehalf-periods and the phase relationship between adjacent periods.
 6. Themethod of claim 4, further comprising providing a second alternatingcurrent added to said first alternating current, having said constantfrequency and a second phase, said second phase shifted 90 degrees fromsaid first phase, for the encoding and transmission of said virtual codewords, wherein said code elements are sent in an uninterrupted series.7. The method of claim 6, wherein said code elements are created basedon characteristics of the sum of said first alternating current and saidsecond alternating current, wherein said characteristics of said sum areselected from the group consisting of the count of like magnitudeperiods, the count of like magnitude half-periods, the duration of likemagnitude periods, the duration of like magnitude half-periods and thephase relationship between adjacent periods.
 8. The method of claim 1,wherein real code words are inserted between said virtual code words,said real code words comprising the same number of bit positions as saidvirtual code words and comprising code words traditionally used totransmit said kinds of information.